The present invention relates to an optical disk player, more precisely relates to an optical disk player, which is capable of restarting to write data from an interruption address even if writing data is once interrupted.
In an optical disk player, data are written on an optical disk. These days, a velocity of writing data on the optical disk is made higher and higher, so that a velocity of transferring data to be written from a host computer to the optical disk player is often slower than the velocity of writing data. This phenomenon is called “buffer under-run”.
In the conventional optical disk player, if writing data is interrupted by buffer under-run, the optical disk cannot be used any longer.
To solve the problem caused by buffer under-run, recently many optical disk players have data protection means so as to prevent producing useless disks.
The data protection means will be explained. When the buffer under-run occurs, the data protection means interrupts writing data and stands by for a while. Then, if a data transferring velocity is accelerated or enough amount of data to be written are stored in a buffer memory, the data protection means restarts writing data.
Therefore, the data protection means can prevent producing useless optical disks even if the buffer under-run occurs.
In the optical disk player having the data protection means, rotation of the optical disk must be synchronized with timing of writing data before restart of writing data so as to securely write data from an interruption address, at which writing data has been interrupted.
Next, the synchronization by the data protection means will be explained. Firstly, the data protection means returns an optical pick-up to a position, whose address is prior to the interruption address, and reads the written data at a reading velocity, which is equal to the writing velocity before the interruption, so as to get EFM (Eight to Fourteen Modulation) signals. Further, the data protection means generates EFM signals for writing data in an encoder and synchronizes the two.
Next, a conventional zone CLV type optical disk player will be explained.
In many conventional optical disk players, data are written on an optical disk by a CLV (Constant Linear Velocity) manner, in which a linear velocity for writing data is fixed. Therefore, the rotation of the optical disk is controlled to write data with fixed pit density.
In the CLV optical disk player, the linear velocity is fixed, so that a rotational speed of the optical disk is made faster when data are written in an inner part of the optical disk; the rotational speed of the optical disk is made slower when data are written in an outer part of the optical disk.
These days, a required data writing velocity is much higher than that of the conventional optical disk players. In the CLV type optical disk player, if the linear velocity is merely accelerated, the rotational speed of the optical disk for writing data in an inner part is too fast to securely write data.
To solve the problem, the zone CLV type optical disk player, which is capable of shortening time for writing data without accelerating the rotational speed of the optical disk for writing data in the inner part, has been produced.
In the zone CLV type optical disk player, data are written in an inner zone of the optical disk at a low constant linear velocity; the linear velocity for writing data is accelerated by stages when the optical pick-up transfers to outer zones to write data therein. Therefore, total time for writing data in the whole optical disk can be shortened.
In the zone CLV type optical disk player too, when the linear velocity is changed, writing data is once interrupted and rotation of the optical disk must be synchronized with timing of writing data before restart of writing data so as to securely write data at higher writing velocity, as well as the data protection means for solving the problems caused by buffer under-run.
Next, the synchronization by zone CLV control means will be explained. The zone CLV control means returns an optical pick-up to a position, whose address is prior to the interruption address, and reads the written data at a writing velocity for next zone, which is faster than the writing velocity before the interruption, so as to get EFM signals. Further, the zone CLV control means generates EFM signals for writing data in an encoder and synchronizes the two.
However, if quality of written data is low due to high writing velocity, correct EFM data patterns cannot be read when the written data are read, so that the rotation of the optical disk and the timing of data to be written cannot be synchronized.
If the synchronization is failed when writing data is restarted, data cannot be written on the optical disk, so that the disk finally becomes a useless disk.
In that case, even if writing data can be restarted, new data cannot be correctly written with respect to the former written data.